Lower Limb - Nerves

Question 1

Which nerve roots form the lumbar plexus?

Answer 1

L1-4 anterior division with contributions from T12

Question 2

Name the terminal branches of the lumbar plexus

Answer 2

Iliohypogastric nerve
Ilioinguinal nerve
Genitofemoral nerve
Lateral Cutaneous nerve
Femoral nerve
Obturator nerve

Question 3

Iliohypogastric nerve

1. 1. Roots
2. 2. Motor functions
3. 3. Sensory functions

Answer 3

1. 1. L1 (contribution T12)
2. 2. Transverse Abdominus, Internal Oblique
3. 3. Posterolateral gluteal skin and pubic region

Question 4

Ilioinguinal nerve

1. 1 Nerve roots
2. 2. Motor function
3. 3. Sensory function

Answer 4

1. 1. L1
2. 2. Transverse Abdominus + IO
3. 3. Superior aspect of anteromedial thigh

Males: skin over the root of penis + anterior scrotum
Females: skin over the mons pubis and labia majora

Question 5

Genitofemoral nerve

1. 1 Nerve roots
2. 2. Motor function
3. 3. Sensory function

Answer 5

1. 1. L1-2
2. 2. Genital branch innervates cremasteric muscle

1.3.
Genital branch - skin over anterior scrotum (males) and mons pubis + labia majora (females)
Femoral branch - skin over anterior aspect thigh

Question 6

Lateral Cutaneous Nerve

1. 1 Nerve roots
2. 2. Motor function
3. 3. Sensory function

Answer 6

1. 1. L2-3
2. 2. Purely sensory
3. 3. Skin over lateral thigh down to knee

Question 7

Obturator Nerve

1. 1 Nerve roots
2. 2. Motor function
3. 3. Sensory function

Answer 7

1. 1. L2-4
2. 2. Obturator Externus, Gracilis, Adductor Longus, Brevis and Magnus (adductor part)
3. 3. Skin of medial thigh

Question 8

Name this nerve (obturator nerve) and describe it’s anatomical course

Answer 8

Formed by the anterior rami nerve roots L2-4 -

descends through psoas major muscle -

travels posterior to common iliac arteries towards obturator foramen -

Enters medial thigh through obturator canal (formed in the obturator foramen by the obturator membrane) -

Divides into anterior and posterior branches -

Anterior branch travels between Adductor Longus and Brevis towards femoral artery -

Posterior division pierces obturator externus muscle + travels between Adductor Brevis and Magnus

Question 9

Which nerve can be damaged during surgery to the abdomen and pelvis?

Answer 9

Obturator Nerve

Question 10

Femoral nerve

1. 1 Nerve roots
2. 2. Motor function
3. 3. Sensory function

Answer 10

1. 1. L2-4
2. 2. Pectineus, iliacus, Satorius, RF and Vastus group
3. 3. Skin to anteriomedial aspect of thigh (anterior cutaneous branch) + medial side of leg and foot (saphenous nerve)

Question 11

Which nerve roots form the sacral plexus?

Answer 11

S1-4 and contributions from L4, 5

Question 12

Superior Gluteal Nerve

1. 1. Nerve roots
2. 2. Motor function
3. 3. Sensory function

Answer 12

1. 1. L4, 5 S1
2. 2. Gluteus Medius, Minimus and TFL
3. 3. Purely motor

Question 13

Inferior Gluteal Nerve

1. 1. Nerve roots
2. 2. Motor function
3. 3. Sensory function

Answer 13

1. 1. L5, S1, 2
2. 2. Gluteus Maximus
3. 3. Purely motor

Question 14

Sciatic Nerve

1. 1. Nerve roots
2. 2. Motor function
3. 3. Sensory function
4. 4. Anatomical course

Answer 14

1. 1. L4-S3
2. 2. Semimembranosis, Semitendinosis, Biceps Femoris, Adductor Magnus (hamstring portion)
3. 3. No direct sensory function

1.4. Exits pelvis via greater sciatic foramen inferior to the piriformis muscle -
Passes posterior to the SG, OI, IG, QF -
Enters thigh passing deep to long head of biceps